Arrangement and embodiment of a spark plug with a diesel reciprocatory piston internal combustion engine

ABSTRACT

A reciprocatory piston internal combustion Diesel engine, which incudes a spark plug which when viewing in the direction of the combustion air flowing at the end of the compression stroke into the combustion chamber provided in the piston is located behind a fuel jet but outside the direct sphere of influence of the fuel jet, while the spark path of said spark plug is located within the region of the piston gap as it exists at the start of the fuel injection, the spark path being protected against air flow by housing means having a maximum of four windows totaling a maximum of half the cicumference of said housing means.

iinite Einstcrwalder States atent 1 [75] Inventor: Gerhard Finsterwalder, Porz-Eil,

Germany [73] Assignee: lKlockner-lllumboldt-Deutz Aktiengesellschaft, Cologne-Deutz, Germany [22] Filed: Sept. 30, 1971 [21] Appl. N0.: 185,159

[52] US. Cl. 123/32 R, 123/32 SP, 123/169 EL, 123/169 PH [51] int. Cl. F02b 3/02 [58] Field of Search 313/138, 139; 123/32 SP, 123/32 R, 169 E, 169 EL, 169 PH, 169 PA, 30 D [56] References Cited UNITED STATES PATENTS 1,361,347 12/1920 Nighswander 313/139 X 1,953,229 4/1934 Heron 123/169 EL 1,987,612 1/1935 Fernandez 313/139 X 2,047,575 7/1936 Burtnett 123/169 EL 2,083,916 6/1937 Mascuch 123/166 PH 1 Aug. 13, 1974 2,150,726 3/1939 Nowosielski 123/169 PH 2,280,972 4/1942 Paulson 123/169 PH 2,344,597 3/1944 Chaston et a1... 123/169 EL 2,391,459 12/1945 Hensel 313/139 2,684,060 7/1954 Schechter 313/138 X 2,803,229 8/1957 Schwaigcr.... 123/32 3,107,658 10/1963 Meurer 123/32 R 3,420,216 1/1969 Meurer et a1. 123/32 FOREIGN PATENTS OR APPLICATIONS 1,196,782 7/1970 Great Britain Primary Examiner-Laurence M. Goodridge Attorney, Agent, or FirmWalter Becker [5 7] ABSTRACT A reciprocatory piston internal combustion Diesel engine, which incudes a spark plug which when viewing in the direction of the combustion air flowing at the end of the compression stroke into the combustion chamber provided in the piston is located behind a 14 Claims, 5 Drawing Figures cylinder H head Pmmm Ans: 31m

ARRANGEMENT AND EMBODIMENT OF A SPARK PLUG WITH A DIESEL RECIPROCATORY PISTON INTERNAL COMBUSTION ENGINE The present invention relates to a diesel reciprocable piston internal combustion engine with a combustion chamber which is provided in a piston and in its basic form is rotation symmetric. At the said combustion chamber the combustion air circulates during the end phase of the compression stroke. More specifically, the present invention relates toa diesel reciprocable piston internal combustion engine of the above mentioned type with an ignition aid in the vicinity of the marginal area of the combustion chamber, and with a fuel injection nozzle the bore or bores of which are directed transverse to the circulating combustion air'in' spaced relationship to the wall of the combustion chamber.

For a considerable time, industry has endeavored to develop reciprocable piston internal combustion engines which can be operated with fuel of very different octane numbers in an optimum manner.

The main difficulty is seen in the shortening of the long ignition delay times of the high octane fuels which makes an ignition combustion impossible in the available short time under ordinary diesel engine conditions. The only means for overcoming these difficulties are high temperatures in the combustion chamber and, more specifically, with all conditions of operation. One way in this direction consists in the increase in the compression in combination with load dependent preheating of the intake air. Such an arrangement, however, has inherent thereto increased stresses in-the structural elements and increased formation of black smoke in gas-oil operation.

A further possibility consists in the creation of a local hot point in the combustion chamber. This may be realized by a glow plug or a spark plug. The spark plug will, for generating the necessary surface temperature, require a high electric power. Moreover, the life of the spark plug is, in view of the continuous temperature load, relatively low and straying to a considerable extent. The spark plug will with a low electric energy consumption and sufficient life span assure a safe ignition possibility also of high octane fuels. For the functioning of a spark plug ignition, it is among others necessary to locate the spark plug in the right spot within the combustion chamber.

A reciprocable piston internal combustion engine has become known in German Pat. No. 1,019,125 according to which a fuel jet in a closed jet form with a respective short free jet length impacts upon the chamber wall at an acute angle in such a way that the thus injected fuel will in the form of a thin film spread and place itself over a large surface and will hold the chamber wall at a temperature which is below the disintegration temperature of the fuel but is located within its boiling range. The fuel adhering tothe wall evaporates up to an ignition to a minor extent whereupon after formation of the flame front, an ever increasing and faster evaporation occurs. The location of the ignition source must with this internal combustion engine expediently be located where first an evaporation of the fuel occurs and where the mixture necessary for the ignition with the combustion air takes place. The evaporation of the fuel first occurs at the marginal area of the fuel film following a short stay in the combustion chamber. As a result thereof, the ignition source must have a considerable distance from the injection nozzle. lnasmuch as the evaporation time depends on the type of the fuel, easily evaporable fuels must be injected" later than heavy evaporable fuels. The time of injection consequently must be changed when chaning the fuel types. Furthermore, the place where the first evaporation occurs likewise changes in conformity with the evaporation speed and thus in conformity with the type of the fuel and fuel mixture so that when selecting the location of the ignition aid a compromise has to be made between the fuel types to be employed. For the first evaporation of the fuel, the temperature of the combustion chamber wall is of foremost importance. Therefore, this temperature, in order to obtain a proper ignition, must be kept in narrow limits.

A reciprocable piston internal combustion engine has become known for instance in French Pat. No. 1,534,228 according to which the combustion air near the end of the combustion stroke circulates in a basically rotation-symmetric combustion chamber providedv in the piston, and the fuel is in the vicinity of the fuel chamber wall and in fine atomized condition injected in a direction transverse to the circulating combustion air, and an ignition aid is so arranged that its hot point or spark path is located shortly behind the nozzle of the injection valve in injection direction approximately at or in the jet mantle of the fuel jet. In this way, the ability of the internal combustion engine to ignite will be increased. The spark plug will directly be hit by the uncommon fuel jet or the drops in the jet mantle will be directly hit.

Experience has shown that with such an arrangement of the spark plug, the spark path can be bridged by, fuel droplets, which fact may bring about faulty ignitionsand failures in the ignitions. Furthermore, the design of the jet mantle changes in conformity with the employed fuel and in conformity with the load on the machine so that the ignition spark will under certain circumstances find no mixture adapted to be ignitable.

It is an object of the present invention to provide a diesel reciprocable piston internal combustion engine which will overcome the above mentioned drawbacks and in particular will make it possible to burn highoctane as well as low-octane fuels in a knock-free manner while avoiding faulty ignitions.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 is a portion of a cross section through the combustion chamber of a diesel reciprocable piston engine for carrying out the method according to the in.- vention.

FIG. 2' is a top view of the combustion chamber in conformity with the arrow ll of HG. 1.

HO. 3 is a view of the injection device and of the ignition source in conformity with the direction III in FIG. 2.

FIG. 4 shows a partial longitudinal section through an ignition aid.

FIG. 5 is a cross section through an ignition aid in conformity with lines V V in FIG. 4.

The diesel reciprocable piston internal combustion engine according to the invention is characterized primarily in that the ignition aid is formed by a spark plug which when viewing, in the direction of the combustion air flowing into the combustion chamber at the end of the compression stroke is located in the vicinity of and behind a fuel jet but outside the direct range of influence of the fuel jet while the spark path of said spark plug is located within the region of the piston gap at the time of the start of the fuel injection, the spark path being protected relative to the air flow by a housing which has up to four perforations, which perforations together amount to at least one-fourth and at the maximum, half of the circumference of said housing.

In view of the arrangement and design of the spark plug, it is possible by means of the reciprocable piston internal combustion engine proved satisfactory for diesel operation and described in the French Pat. No. 1,534,228, to combust also high-octane fuels. By the air which spirally flows into the combustion chamber from the piston gap due to the radial movement superimposed upon the twist flow, first the finest droplets of the fuel jet injected in a transverse flow are blown away and are evaporated after a short flow distance. The spark plug, which is not to be directly hit by the fuel jet, is so far remote from the fuel jet and extends only to such an extent in the combustion chamber that only fuel vapor-air mixture with A approximating l reaches said spark plug. Inasmuch as the spark plug is located in strong air whirls, steps have to be taken which will prevent a blowing out of the spark and of the flame being formed. To this end, the spark path is protected relative to the air flow by a housing which has up to four perforations or passages which together amount to at least one-fourth and at a maximum to half the circumference of said housing. With such a design, it has been found to be particularly advantageous to have the spark plug equipped with a cylindrical central electrode and with a mass electrode which at the face side covers the central electrode while the axis of said spark plug is located within an imaginary cone having a 40 cone angle, the axis of said cone being substantially parallel to the longitudinal axis of the piston.

According to a further development of the invention, it is suggested that the distance of the spark path from the cylinder head bottom is within the range of from 2.5 to 5 millimeters. With these values, with customary twist figures for the air movement and with finest atomizing injection nozzles, very good combustion values can be realized.

ln order to prevent that in case of assembly errors and lack of precision in the manufacture of the injection nozzle, larger fuel droplets reach the spark path, it is suggested according to a further development of the invention that the lantern-shaped housing of the spark plug has two perforations which each extend over 90' of the circumference and a remaining housing part points to the fuel injection nozzle. In this way, there is realized that as the case may be, larger not yet evaporated fuel droplets impact upon the remaining housing part and will there evaporate in view of the high temperature. With this embodiment, also the ratio of the heat absorbing surface to the heat withdrawing or conducting transverse sections is very favorable, which fact contributes to an increase in the life span of the spark plug.

In order to reach a long life span of the ignition spark, the admissible minimum electrode distance is of importance. This influence depends on the temperature of the electrode. The higher this temperature, the less must be the spacing between the electrodes without leading to a delayed combustion or engine miss in the ignition. Since, however, high electrode temperatures bring about a faster burning off, the electrode spacing cannot be selected randomly small. Expansion differences between central and mass electrode may at certain conditions of operation lead to faulty ignitions. For purposes of obtaining an optimum, according to a further development of the invention, it is suggested that the central electrode of the spark plug is at its face side provided with a small conical recess 23. The electric breakdown by surface conduction occurs only in the narrowest gap on the circumference of the electrode from where the flame can well spread. Only with increasing burning off of the marginal area, the spark advances more and more toward the center of the electrode. The widening gap will find good conditions of expansion or spreading for the flames which originate at the center of the electrode.

The life of the spark plug and its function safety will to a great extent be dependent on the selected materials. It has proved that according to a further design of the invention, such spark plugs are particularly advantageous with which the mass electrode consists of low alloyed steel which is protected by alighting siliconizing or chromium plating and which toward the spark path has a thin plate of platinum iridium at a ratio of approximately /10, said plate may for instance be gold soldered in vacuum. A further improvement of the engine according to the invention is obtained when the central electrode likewise has a thin plate of platinum iridium at a ratio of 90/10 which plate may be gold soldered in a vacuum.

The 3 millimeter thick closure plate forming the mass electrode is within the range of the perforations circular arc-shaped whereby in an advantageous manner the flow of the mixture is conveyed toward the spark path. The electrode temperature important for the electrode burning off may with the central electrode be sunk (gesenkt) by a two-material electrode with copper or silver core and steel mantle.

Referring now to the drawings in detail, the arrangement shown therein comprises a piston l of a reciprocable piston internal combustion engine, which piston has arranged therein a combustion chamber 2 which in its basic form is rotation-symmetric. The combustion chamber 2 has a basically cylindrical form, and its longitudinal axis 10 is inclined to the longitudinal axis 11 of the piston 1. Near the end of the compression stroke, combustion air circulates in said combustion chamber 2. Transverse to the circulating combustion air, shortly prior to the piston reaching its upper dead center point, the fuel will in fine atomized condition by an injection device 5 be injected into an area close to the wall 3 of the combustion chamber 2, and the thus injected fuel is ignited by means of an ignition aid 4 for instance a spark plug. The injection of the fuel is effected near that side of the combustion chamber 2 which has the longest straight mantle line. in view of the fine atomization of the fuel injected into the marginal zone of the combustion chamber 2, a reaction-slow fuel-air mixture ring is formed. The fuel jets 6 leaving the injection device 5 are picked up and carried around by the rotating combustion air, and the marginal zone of said fuel jet 6 will be blown away. Above the combustion chamber 2 within the region of the piston gap 7, a spiralshaped current of the combustion air will form which results from the displacement of the rotary movement with a radially directed transverse current. The flow direction of the combustion air in the piston gap 7 is indicated by arrows 8.

The ignition aid 4 is in conformity with the present invention, when viewing in the direction of flow of the combustion air, flowing into the combustion chamber along spiral paths, located behind one of the fuel jets 6 but outside its direct range of influence and its spark path 9 is located within the region of the piston gap 7 which exists at the start of the injection. The ignition is initiated simultaneously with the fuel injection. For purpose of a finer atomization of the fuel,'it is expedient to employ an injection device 5 with a plurality of nozzle bores the longitudinal axes of which are located within a 30 cone as shown in FIG. 3. However, it is also possible to employ injection devices with one nozzle bore. The ignition aid 5, for instance a spark plug, has a cylindrical central electrode with a core 13 of good heat conducting material. This core 13 is surrounded by a sleeve 14 of a material of higher strength. At the end face side, the core 13 is, toward the spark path 9, connected to a plate 15 of an alloy of platinum iridium at a ratio of 90/10. Sleeve 14 and plate 15 are under a vacuum soldered to the central electrode 12. The outer housing 17 of the spark plug is separated from the central electrode by an insulating body 16. Within the region of the end of the central electrode, the housing 17 has a lantern-like contour. The two passages 18 in said housing 17 occupy each a circumferential portion of 90 and are so designed that their contour 21 when viewed in the longitudinal section of the housing corresponds to an arc. The closure plate of the lanternshaped housing 17, which at the end face side is approximately 3 millimeters thick, and which forms the mass electrode 19, has inserted thereinto a plate of a platinum-iridium alloy. This plate is inserted and soldered to the mass electrode in such a way that within the region of the passages 18 the circumference of the plate 20 is surrounded by a wide margin 22 of approximately 0.5 millimeters.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawings but also comprises any modifications within the scope of the appended claims.

What I claim is: j

1. In combination in a reciprocatory piston internal combustion engine: a cylinger head, a reciprocable piston movable toward and away from said cylinder head and having a recess therein forming a combustion chamber for receiving circulating combustion air during the end phase of the compression stroke of said piston, said combustion chamber having a basically rotation symmetric contour and having a combustion chamber axis inclined with regard to the axis of said piston so that said combustion chamber in its axial direction has a longest wall portion and an oppositely located shortest wall portion, an injection nozzle supported by said cylinder head and having a mouth the axis of which extends in spaced relationship to said longest wall portion of said combustion chamber but closer to the latter than to said shortest wall portion of said combustion chamber, said axis of said mouth also extending transverse to the direction of flow of the circulating combustion air received by said combustion chamber during the end phase of the compression stroke of said piston, a spark plug arranged closely behind a fuel jet from said injection nozzle when viewed in the direction of flow of the combustion air entering said combustion chamber during the end phase of the compression stroke, said spark plug being located outside the direct sphere of influence of the fuel jet from said injection nozzle, and the spark path being located within the region of the gap between said piston and said cylinder head at the time of the start of the fuel injection, said spark plug including longitudinal housing means comprising a tubular external wall closed at one end by a transverse wall forming a mass electrode and a longitudinal central electrode having its end spaced from said transverse wall to provide a spark gap, said tubular wall having not more than four windows adjacent said spark gap extending for a total of not more than one-half of the circumference of the wall to leave wall portions between said windows which extend for at least one-half the circumference to limit any liquid fuel and said spark gap while allowing access of the combustion mixture, in which one of said wall portions lies between said spark gap and said injection nozzle.

2. An engine in combination according to claim 1, in which the spacing of the spark path from the bottom of the cylinder head is within the region of from 2.5 to 5 millimeters.

3. An engine in combination according to claim 1, in which said housing means has two windows each extending over an angle of at the circumference of said housing means, the remaining circumferential housing means portion between said windows facing toward said injection nozzle.

4. An engine in combination according to claim 1, in which said central electrode at the end face thereof is provided with a small conical recess.

5. An engine in combination according to claim 1, in which said mass electrode is made of low alloyed steel and comprises a thin plate of platinum-iridium of a ratio of approximately 90:10, said plate facing toward the spark path and being vacuum soldered to said mass electrode.

6. An engine in combination according to claim 5, in which said alloyed steel is aluminized.

7. An engine in combination to claim 5, in which said alloyed steel is chromized.

8. An engine in combination to claim 5, in which said alloyed steel is siliconized.

9. An engine in combination to claim 5, in which said mass electrode between said soldered plate and the outer circumference of said mass electrode within the region of said windows has a margin of approximately 0.5 millimeters.

10. An engine in combination according to claim 5, in which said central electrode opposite said thin plate of said mass electrode has a thin plate of platinumiridium of the ratio 90:10 vacuum soldered to said central electrode.

11. An engine in combination to claim 10, in which said central electrode has an inner core of good heat conductive substance connected to said thin plate of said central electrode.

12. An engine in combination to claim 1, in which said central electrode and said mass electrode are spaced from each other by a distance of from 0.15 to 0.6 millimeters.

13. An engine in combination according to claim 1, in which said mass electrode comprises a closure plate closing off said housing means and having a thickness of approximately 3 millimeters.

14. An engine in combination according to claim 1, in which the windows of said housing means in the longitudinal section thereof have the contour of an arc. 

1. In combination in a reciprocatory piston internal combustion engine: a cylinger head, a reciprocable piston movable toward and away from said cylinder head and having a recess therein forming a combustion chamber for receiving circulating combustion air during the end phase of the compression stroke of said piston, said combustion chamber having a basically rotation symmetric contour and having a combustion chamber axis inclined with regard to the axis of said piston so that said combustion chamber in its axial direction has a longest wall portion and an oppositely located shortest wall portion, an injection nozzle supported by said cylinder head and having a mouth the axis of which extends in spaced relationship to said longest wall portion of said combustion chamber but closer to the latter than to said shortest wall portion of said combustion chamber, said axis of said mouth also extending transverse to the direction of flow of the circulating combustion air received by said combustion chamber during the end phase of the compression stroke of said piston, a spark plug arranged closely behind a fuel jet from said injection nozzle when viewed in the direction of flow of the combustion air entering said combustion chamber during the end phase of the compression stroke, said spark plug being located outside the direct sphere of influence of the fuel jet from said injection nozzle, and the spark path being located within the region of the gap between said piston and said cylinder head at the time of the start of the fuel injection, said spark plug including longitudinal housing means comprising a tubular external wall closed at one end by a transverse wall forming a mass electrode and a longitudinal central electrode having its end spaced from said transverse wall to provide a spark gap, said tubular wall having not more than four windows adjacent said spark gap extending for a total of not more than one-half of the circumference of the wall to leave wall portions between said windows which extend for at least one-half The circumference to limit any liquid fuel and said spark gap while allowing access of the combustion mixture, in which one of said wall portions lies between said spark gap and said injection nozzle.
 2. An engine in combination according to claim 1, in which the spacing of the spark path from the bottom of the cylinder head is within the region of from 2.5 to 5 millimeters.
 3. An engine in combination according to claim 1, in which said housing means has two windows each extending over an angle of 90* at the circumference of said housing means, the remaining circumferential housing means portion between said windows facing toward said injection nozzle.
 4. An engine in combination according to claim 1, in which said central electrode at the end face thereof is provided with a small conical recess.
 5. An engine in combination according to claim 1, in which said mass electrode is made of low alloyed steel and comprises a thin plate of platinum-iridium of a ratio of approximately 90:10, said plate facing toward the spark path and being vacuum soldered to said mass electrode.
 6. An engine in combination according to claim 5, in which said alloyed steel is aluminized.
 7. An engine in combination to claim 5, in which said alloyed steel is chromized.
 8. An engine in combination to claim 5, in which said alloyed steel is siliconized.
 9. An engine in combination to claim 5, in which said mass electrode between said soldered plate and the outer circumference of said mass electrode within the region of said windows has a margin of approximately 0.5 millimeters.
 10. An engine in combination according to claim 5, in which said central electrode opposite said thin plate of said mass electrode has a thin plate of platinum-iridium of the ratio 90:10 vacuum soldered to said central electrode.
 11. An engine in combination to claim 10, in which said central electrode has an inner core of good heat conductive substance connected to said thin plate of said central electrode.
 12. An engine in combination to claim 1, in which said central electrode and said mass electrode are spaced from each other by a distance of from 0.15 to 0.6 millimeters.
 13. An engine in combination according to claim 1, in which said mass electrode comprises a closure plate closing off said housing means and having a thickness of approximately 3 millimeters.
 14. An engine in combination according to claim 1, in which the windows of said housing means in the longitudinal section thereof have the contour of an arc. 